1. FIELD OF THE INVENTION
The present invention relates to a blow-by gas circulating system for a 4-cycle engine.
2. DESCRIPTION OF THE PRIOR ART
A blow-by gas circulating systems for a 4-cycle engine generally includes a crank case, a valve chest in cylinder head, and an oil separating chamber in a wall surface of a cam chamber or the like in a cylinder block. To prevent an oil mixed into a blow-by gas from entering into the oil separating chamber, it is desirable to provide the oil separating chamber at a position as high as possible in a normal operational attitude of the engine.
In a vertical crankshaft type 4-cycle engine with a crankshaft disposed substantially vertically, a cylinder head and a crank case are level with each other and hence, the provision of the oil separating chamber is not always adjacent the cylinder head, and in some cases, the oil separating chamber may be provided on an upper wall surface of the crank case (see Japanese Utility Model Application Laid-open No. 155,935/78 and Japanese Patent Publication No. 26,247/88).
It is also known that the oil separating chamber and an intake system are interconnected by a blow-by gas passage, so that a fuel mist is prevented from being released into the atmosphere (see Japanese Utility Model Application Laid-open No. 60,438/80 and Japanese Utility Model Publication No. 24,739/87).
In the device described in the above-described Japanese Utility Model Application Laid-open No. 60,438/80, the blow-by gas passage is connected to a connecting pipe mounted upstream of a carburettor, but because the blow-by gas passage partially overlie a mounting portion of the connecting pipe to the carburettor, there is a possibility that the connecting pipe mounting operation is obstructed by the blow-by gas passage.
In a single-cylinder vertical crankshaft type engine as described in Japanese Patent Publication No. 26,247/88, when the intake and exhaust systems are put in two, the intake system being located sideways of or slightly above the engine, there is a need for a provision for preventing the interference of an upper surface of the engine with a rotor such as a flywheel in connecting the blow-by gas passage to the intake system. However, in the device in which the blow-by gas passage is partially loosened in the middle of extension toward the intake system, as illustrated in FIG. 1 in Japanese Utility Model Publication No. 24,739/87, there is a possibility that the oil deposited on an inner wall surface of the blow-by gas passage flows from the intake system into a combustion chamber to exert an influence to the combustion state.
Even in the engine described in Japanese Utility Model Application Laid-open No. 155,935/78, there is likewise a need for a provision for making it difficult for the oil to be accumulated in the blow-by gas passage.